Telemetry: instrument auth and workspace lifecycle

[EhabY]

Part of the Telemetry Phase A rollout. See the RFC in Linear: AIGOV-154.

Events

• auth.token_refresh with result, trigger, measurement durationMs.
• auth.intercept_401 with recovery.
• auth.login_prompt with trigger, result.
• workspace.start with result, measurement durationMs. Emitted when the user opens a workspace and it transitions to running.
• workspace.stop with trigger (user, idle).
• workspace.update.triggered with result, measurement durationMs.

Sites

• src/oauth/sessionManager.ts refresh path.
• src/api/authInterceptor.ts 401 handling.
• src/login/loginCoordinator.ts login-dialog path.
• Workspace-related command handlers (start, stop, update).

Tests

• TestSink assertions for each event.
• Token refresh emits on both background and reactive triggers.
• 401 path emits with the right recovery value for the refresh-success and login-required cases.
• Workspace start emits on successful transition to running, error event on failure.

Depends on AIGOV-243, AIGOV-273.